Urinary System

4 Components of Urinary System

1) kidneys

2) ureters

3) urinary bladder

4) urethra

One of the primary functions of kidneys is…?

to filter blood and convert filtrate to urine

Urinary Tract 3 Components

1) ureters

2) urinary bladder

3) urethra

Urinary Tract main function

transport urine from kidneys to outside the body

What 5 Process occur in the kidney as filtrate is being converted to urine?

1) elimination of metabolic waster

2) regulation of ion levels

3) regulation of acid-base balance

4) regulation of BP

5) elimination of biologically active molecules

Elimination of Metabolic Waste in the Kidneys

kidneys remove waste in filtrate (urea, uric acids) to prevent substance from reaching toxic levels in blood

Regulation of ion Levels in Kidneys

kidneys control Na+, K=, Ca+. phosphate ions by eliminating diff amounts in urine, depends on dietary intake

Regulation of Acid Base Balance in Kidneys

alter amounts of H+ and bicarbonate HCO3- ions in blood by elimination through urine

Regulation of BP in Kidneys

regulate through excreting fluid in urine, release renin enzyme which produces angiotensin II hormone that increases BP, one of the most important functions is regulation of BP by kidneys

Elimination of Biologically Active Molecules in Kidneys

small molecules (hormones, drugs) filtered from blood and become part of urine

Other 3 Functions of Kidneys

1) formation of calcitriol

2) production and release of EPO

3) potential to engage in gluconeogenesis

Formation of Calcitriol in Kidneys

kidneys synthesize final enzyme in calcitriol (active D3) hormone formation, increase absorption of Ca from SI to increase blood Ca concentration

Production and Release of EPO in Kidneys

kidneys measure O2 levels as they filter blood, secrete EPO if low blood O2 levels, stimulates red bone marrow to increase erythrocyte formation

Engaging in Gluconeogenesis in Kidneys

may occur during prolonged fasting or starvation convert glucose from non-carb sources, help maintain healthy blood glucose in periods of extreme nutrient deprivation

Kidney Hilum

concave medial border, where vessels, nerves, and ureter connect to the kidney

Kidney lateral border

called the convex

Kidney and Adrenal Glands

the adrenal glands lie superior to the kidneys

Kidney Location

along the posterior abdominal wall, lateral to vertebral column

Left Kidney Location

between the T12 and L3 vertebrae

Right Kidney Location

2cm inferior to the left kidney to accommodate the large size of the liver

Kidney Protections

both kidneys only partially protected by rib cage, they are vulnerable to forceful blows to the inferior region of back

Kidney Peritoneum

retroperitoneal ,posterior to parietal peritoneum, only the anterior surface is covered

Innermost to Outermost 4 Tissue Layers of Kidney

1) fibrous capsule

2) perinephric fat

3) renal fascia

4) paranephric fat

Fibrous Capsule of Kidney

adheres to external surface of kidney, composed of tough dense irregular CT, maintains kidney shape, protects it from trauma, and helps prevent infectious pathogens from infecting kidney

Perinephric Fat of Kidney

external to fibrous capsule, also called perineal fat or adipose capsule, contains adipose CT, cushion and stabilizes kidney

Renal Fascia of kidney

external to perinephric fat, composed of dense irregular CT, anchors kidney to surrounding structures

Paranephric Fat in Kidney

pararenal fat/paranephric body, outermost layer, composed of adipose CT and provides cushion and stability to kidney

Renal Columns

extension of cortex, project into medulla and subdivide it to renal pyramids (appear striated(

Corticomedullary Junction

where the wide base of renal pyramid lying at the edge of the medulla meets the cortex

Renal Papilla

the medially directed apex (tip) of renal pyramid

Renal Lobes

divided kidneys, 8-15, consist of renal pyramid, portions of renal columns adjacent to either side of renal pyramid, and renal cortex external to pyramid base

Renal Sinus

medially located, serves as urine drainage area, organized to minor/major calyces and renal pelvis

Minor Calyces

each 8-15 funnel shaped minor calyces associated with a renal pyramid

Major Calyx

where minor calyx merge to, each kidneys has 2-3 major calyces

Renal Pelvis

where the major calyces merge to, renal pelvis is at medial edged of kidney with ureter, houses renal artery, renal vein, lymph vessels, nerves, variable amount of fat

Kidney Innervation

by both sympathetic and parasympathetic division of ANS

Kidney, Sympathetic Nerves

from T10-T12 segments of spinal cord to innervate BVs of kidney, include smooth muscle in walls of afferent and efferent arterioles, and juxtaglomerular apparatus

Effect of Sympathetic Kidney Stimulation

decrease urine production

Parasympathetic Nerves to Kidney

extend from brain within vagus nerve, no known effect

Nephron Structure

microscopic functional filtration unit of kidney

Nephron 2 Components

1) renal corpuscle

2) renal tubule

Renal Corpuscle

composed of glomerulus and glomerular capsule

Renal Tubule

composed of PCT, nephron loop, and DCT

Renal Corpuscle and Renal Tubule Location

almost all reside in the cortex of the kidney

Renal Corpuscle

enlarge round portion of nephron housed in the renal cortex

Glomerulus

thick tangle of blood capillary loops

Blood in Glomerulus

enters by afferent arteriole and exits by efferent arteriole

Glomerular (Bowman) Capsule

formed by internal permeable visceral layer overlaying glomerulus and external impermeable parietal layer of simple squamous

Capsular Layer

between the visceral and parietal layer of glomerular capsule, receives filtrate then modified to make urine

Renal Corpuscle Poles

1) Vascular Pole

2) Tubular Pole

Vascular Pole

where afferent and efferent arterioles attach to glomerulus

Tubular Pole

where the renal tube originates

Renal Tubule

microscopic, simple epithelium resting on basement membrane, PCT, nephron loop, and DCT sections (tubules in vortex, loop extends from cortex into medulla)

PCT

first region of renal tubule, originates at renal corpuscle, simple cuboidal, microvilli to increase SA and reabsorption

Nephron Loop

originates at sharp bend in proximal convoluted tubule, ascending and descending limb in medulla

Descending Limb

extend from PCT to tip of nephron loop

Ascending Limb

extends from tip of nephron loop to DCT

Thick Segments of Loop

simple cuboidal epithelium

Thin Segments of Loop

simple squamous epithelium

DCT

originates in renal cortex at end of nephron loops’ thick ascending limb, extends to collecting tubule, simple cuboidal, short microvilli, not fuzzy under microscope

2 Types of Nephrons

1) Cortical Nephrons

2) Juxtamedullary Nephrons

Cortical Nephrons

near edge of cortex, short nephron loop barely penetrating medulla, most in cortex, 85% of nephrons are in this category

Juxtamedullary Nephrons

long nephron loop deep to medulla, establish salt concentration gradient in interstitial space outside loop, collecting tubules, and ducts, regulation of urine concentration by ADH

Collecting Tubule

where nephrons drain into, tubules empty to collecting ducts

Collecting Tubule and Ducts Projection

through renal medulla toward renal papilla

Papillary Duct

where collecting ducts empty, in the renal papilla, most distal portion of collecting ducts, empty into minor calyx

Epithelial Cells of Collecting Tubules

cuboidal shaped, become columnar in ducts near renal papilla

Striations in Renal Pyramids

formed by straight ascending and descending tubules of nephron loops and collecting ducts

Principal Cells

specialized epithelial, target cells for aldosterone and ADH in collecting tubules and collecting ducts

Intercalated Cells in Collecting Tubules/Ducts

type A/B, regulated urine and blood pH, type A also regulate K+ in blood

Juxtaglomerular Apparatus

located where afferent arteriole and DCT are in contact, close to glomerulus

2 Functions of JG Apparatus

1) control urine formation

2) regulate BP

3 Structures of JG Apparatus

1) granular cells

2) mascula densa

3) extraglomerular mesangial cells

Granular Cells

modified SM cells in wall of afferent aretiole

Granular Cell 2 Functions

1) contract when stimulated by stretch or sympathetic division of ANS

2) synthesize, store and release renin

Renin

needed in production of angiotensin I and converted to angiotensin-converting enzyme ACE to angiotensin II

Mascula Densa

epithelial cells in DCT, located in tubule wall adjacent to granular cells of afferent arteriole, narrower and taller than other DCT cells

Mascula Densa Functions

1) detect changes in NaCl of tubular fluid in lumen of DCT

2) signal granular cells in afferent arteriole to release renin through paracrine stimulation

Extraglomerular Mesangial Cells Location

outside glomerulus in gap between afferent and efferent arteriole

Extraglomerular Mesangial Cells Function

communicate with other cells of JG apparatus by gap junctions and release paracrine hormones, play role in release of renin

Cardiac Output and Kidney

at least 20 to 25% of resting cardiac output flows through kidneys to remove unwanted substances

Filtrate Formation

when blood flows through glomerulus and some components of plasma enter capsular space

Renal Artery

delivers blood to each kidney, arises from abdominal aorta

Segmental Arteries

formed when renal artery branches in the renal sinus

Interlobar Arteries

formed when segmental arteries branch in renal sinus, located between renal lobes in the renal columns

Arcuate Arteries

formed when interlobar arteries extend to corticomedullary junction and branch, project parallel to base of medullary pyramid at junction

Interlobular Arteries

formed from arcuate artery branches that project peripherally into cortex where renal lobules are located

Afferent Arterioles

formed as interlobular arteries extend to cortex and branch, each supplies blood to glomerulus which filters some blood plasma

Efferent Arteriole

where most blood which was unfiltered exits the glomerulus, branches to peritubular capillaries or vasa recta (gas exchange with kidney and blood)

Peritubular Capillaries

intertwines around PCT and DCT, primarily in cortex of kidney

Vasa Recta Capillaries

straight vessels in nephron loop, mainly in the medulla of kidney

Peritubular and Vasa Recta Capillaries Drainage

drain into network of veins

Interlobular Veins

smallest of the kidney veins

Arcuate Veins

merged from interlobular veins, at base of medullary pyramids

Interlobar Veins

merged from arcuate veins, extend through renal columns

Renal Vein

merged from interlobar veins in renal sinus, extends from kidney at its hilum, drains blood into iVC

Filtrate

when blood flows through glomerulus and is filtered water and solutes move from blood plasma across filtration membrane into capsular space to form filtrate

Tubular Fluid

filtrate enters PCT and is called tubular fluid

Tubular Fluid Movement

PCT to nephron loop to DCT, enter small collecting tubules that empty to collecting ducts